Steel beam coupling device

ABSTRACT

A coupling device for connecting members, including: a coupling case that has a plurality of connecting slots which respectively receive the members; and wedges that are inserted into the spaces between the coupling case and each of the members perpendicularly to the direction of external pressure given to each of the members. Each of the wedges have one side and another side out of at least a couple of slope sides contacting the coupling case in opposite directions and have a higher coefficient of friction on a bottom side surface that touches one of the members than on the slope side surface that touches the coupling case.

TECHNICAL FIELD

The present invention relates to a coupling device for structuralmembers to transfer load from one member to another. The coupling devicecomprises a coupling case that contains connecting slots in which themembers to be connected are placed and wedges that are inserted in thespace between the coupling case and the connected members. The couplingdevice of the present invention can connect structural members using thewedging action under external forces. To prevent the members fromslipping out of the coupling case, the surface of the wedge that touchesthe connected member is treated to have a higher coefficient of frictionthan the surface that touches the coupling case.

BACKGROUND ART

Bolt connection has been widely used as the means of structuralconnection in construction fields. As illustrated in FIG. 1, boltconnection connects two members (10) by inserting bolts (14) into theholes in the members and the splice plates (12) and tightening the nuts(15).

However, bolt connection requires a large number of holes to be drilledin the connected members and the splice plates, and this causes problemssuch as a notch or stress concentration around the holes.

Furthermore, since the holes are drilled larger than the bolt diameterto meet the dimensional tolerance during erection, slip of theconnection may occur and result in undesirable performance when thejoint is subjected to repeated reversed load as shown in FIG. 2. Inorder to prevent slip from occurring, friction-type connection has beenused. In the friction-type connection, high clamping force is induced bytightening the nuts sufficiently and the connection resists load by thefriction force between the connected member and the splice plates.However, the specified pretension force is not easy to obtain andinstallation of bolts increases the construction costs.

To improve the performance of bolt connection, Korean Laid-open Pat. No.1999-76051 (Application No. 10-1998-10689) has disclosed a connectingtechnique in which friction rings (16) are placed between the connectedmember (10) and the splice plates (12) to increase the frictional force(See FIG. 3). Likewise, Korean Laid-open Pat. No. 1998-72021(Application No. 10-1998-28349) has disclosed another connectingtechnique in which the surfaces of connected member (10) and the spliceplates (12) are treated to have serrations to increase the frictionalforce (See FIG. 4).

The proposed methods may increase the frictional force but can not solvethe problems of bolted connection. Moreover, friction rings make a gapbetween the connected member and the splice plates, which may impair theintegrity of the joint. Mechanically processing the surfaces to haveserrations may increase the fabrication costs.

DISCLOSURE OF INVENTION

It is the objective of the present invention to provide an economicalcoupling device for structural connections that is easy to install andhas a good structural performance.

The coupling device of the present invention can solve the problems ofthe bolt connection by reducing or excluding the use of bolts usingwedging action.

The coupling device of the present invention has characteristicsdescribed hereinafter.

The coupling device comprises a coupling case that contains connectingslots in which the members to be connected are placed and wedges thatare inserted into the space between the coupling case and the connectedmembers.

In addition, the surface of said wedge which touches said member istreated to have a higher coefficient of friction than the surface whichtouches said coupling case.

The sectional shape of said wedge could be selected among triangle,trapezoid, and pentagon to conform in shape to the space between saidcoupling case and said members.

Said wedge has a feature that the angle (θ) between the slope side andthe bottom side is ranged from 1° to$\left( {{atan}\frac{\mu^{\prime} - \mu}{1 + {\mu \cdot \mu^{\prime}}}} \right)$(where μ is a coefficient of friction between said wedge and saidcoupling case, and μ′ is a coefficient of friction between said wedgeand said members).

The bottom surface of said wedge has a feature that it is treated toincrease the coefficient of friction. Particularly, said bottom surfacemay be processed mechanically to have serrations of various shapes.

Contrary, the slope surface of said wedge has a feature that it istreated to reduce the coefficient of friction. Precisely, said slopesurface may be finished mechanically and/or coated with a lubricant.

If said coupling case is a separate-type, it has a feature that the twoparts are joined using bolts or using male piece having projection part(herein after male piece) and female piece having furrow part (hereinafter female piece). In the latter case, a male piece slips into afemale guide (the male and female pieces can be tapered to helpinstallation).

As depicted in FIG. 6, an elastic clipping plate can be used for joiningsaid wedge and said member in firm contact. Springs, screws, and thelike can be used for the same purpose.

The coupling device of the present invention will be clearly describedin reference to the following drawings hereinafter. However, thesedrawings are for illustration purpose, and modification and improvementcan be made in the scope of the present invention.

FIG. 5 illustrates the principle of operation for the coupling device ofthe present invention.

In FIG. 5, θ is the angle between the bottom side (304) and the slopeside (302) of the wedge; μ is the coefficient of friction between theslope surface of the wedge (302) and the coupling case (20); μ′ is thecoefficient of friction between the bottom surface of the wedge (304)and the connected member (10); P′ is the externally applied load actingon the connected member (10); P is the vertical force induced by P′ dueto the wedging action (P increases proportionally as P′ increases).

Force equilibrium along the slope side of the wedge requires$\begin{matrix}{{{2\left( {\frac{P^{\prime}}{2}\cos\;\theta} \right)} - {2P\;\sin\;\theta}} = {2\;{\mu\left( {{\frac{P^{\prime}}{2}\sin\;\theta} + {P\;\cos\;\theta}} \right)}}} & (1)\end{matrix}$where $\frac{P^{\prime}}{2}\cos\;\theta$is the component of force P′ in the slope direction; Psinθ is thecomponent of force P in the slope direction;$\mu\left( {{\frac{P^{\prime}}{2}\sin\;\theta} + \;{P\;\cos\;\theta}} \right)$is the frictional force along the slope surface.

Solving Equation (1) for P′ gives $\begin{matrix}{{P^{\prime} = {2P}}\frac{{\sin\;\theta}\; + {\mu\;\cos\;\theta}}{{\cos\;\theta}\; - {\mu\;\sin\;\theta}}} & (2)\end{matrix}$

In order to prevent the connected member from slipping out of thecoupling case, the frictional resistance acting on the contact areabetween the bottom surface of the wedge (304) and the connected member(10) is required to exceed the external load. This requirement may bewritten as P′<2Pμ′.

Using Equation (2), this requirement becomes $\begin{matrix}{\frac{{\sin\;\theta} + {\mu\;\cos\;\theta}}{{\cos\;\theta}\; - {\mu\;\sin\;\theta}} < \mu^{\prime}} & (3)\end{matrix}$

Solving Equation (3) for θ gives $\begin{matrix}{\theta\; \prec {a\;\tan\frac{\mu^{\prime} - \mu}{1 + {\mu \cdot \mu^{\prime}}}}} & (4)\end{matrix}$

Consequently, the angle θ is calculated by substituting μ and μ′ valuesinto the equation (4) and then the shape of the wedge (10) is determinedto have a lower value than the calculated θ considering the safetyfactor for the structure.

Namely, when external forces such as tension, compression and shearingforce are acted on the member (10), as the external force increases, thevertical force that is induced to the member (10) by the wedge (30)increases due to the difference between the coefficient of friction μbetween the slope side (302) of the wedge (30) and the coupling case(20) and μ′ between the bottom side (304) of the wedge (30) and themember (10). As a result, the frictional force between the member (10)and the wedge (30) depends on the maximum capacity of said coupling case(20) to resist the vertical force.

The size and the shape of the wedge (30) is determined depending on thevalue of θ. As the difference in the values of the friction coefficientsμ and μ′ increases, the larger value of the angle θ can be used. As thevalue of θ increases, the force that the coupling case has to resist invertical direction reduces, which helps to reduce the size of thecoupling case. This is why the μ value of the slope surface (302) of thewedge (30) needs to be reduced by finishing mechanically or coating withlubricants. At the same time, the μ′ value needs to be increased bymechanically processing the bottom surface (304) of the wedge (30) tohave serrations of various shapes. The examples of the serrations aredemonstrated in FIG. 8.

In the specification of the present invention, the term “member (10)” isused to represent the members to be connected such as structural steelH-shaped sections. However, It can be made of any material such as wood,plastic, and stone. Likewise, the coupling case (20) and the wedge (30)can be made of steel preferably, but also of any material such as wood,plastic, stone, and so on.

The term “connecting slot (22)” designates the slots made in thecoupling case (20) where the member (10) and the wedge (30) are placedfor connection. The term “connecting slot (22)” is described andindicated hereafter without the symbol of the figure

FIG. 6 shows the installation of the coupling device of the presentinvention when external force P acts in the direction shown in thefigure. The upper one is an illustration of the dismantled state and thelower one is an illustration of the assembled state.

As demonstrated in FIG. 6, when two members (10) are connected in orderto resist force P that acts in the direction shown in the figure, thecoupling case (20) is incorporated between two members (10). After themembers are placed in the connecting slots of coupling case (20) (thesymbol of the figure not denoted), wedges (30) are inserted into thespace between the coupling case and the members in the direction that isperpendicular to the direction of the external force. To join the wedgeand the member in firm contact, an elastic clipping plate (40) can beused as shown in FIG. 6. Elastic clipping plates are not shown but canbe used in other figures.

The wedges (30) are made to have a proper angle between the slope sideand the bottom side, which is determined from Equation (4). In theassembled state, the members (10) do not slip out of the coupling case(20) under external force P acting in the direction shown in the figuredue to the wedging action of the wedge (30). As the external forceincreases, the higher clamping force is induced in the verticaldirection and the frictional force increases proportionally.

FIG. 7 shows the installation of the coupling device according to thepresent invention when external force P acts in the direction shown inthe figure. The upper one is an illustration of the dismantled state andthe lower one is an illustration of the assembled state.

As demonstrated in FIG. 7, when two members (10) are connected in orderto resist force P that acts in the direction shown in the figure, thecoupling case (20) is incorporated between two members (10). After themembers are placed in the connecting slots of coupling case (20) (thesymbol of the figure not denoted), wedges (30) are inserted into thespace between the coupling case and the members (10) in the directionthat is perpendicular to the direction of the external force.

The wedges (30) are made to have a proper angle between the slope sideand the bottom side, which is determined from Equation (4). In theassembled state, the members (10) do not slip out of the coupling case(20) under external force P acting in the direction shown in the figuredue to the wedging action of the wedge (30). As the external forceincreases, the higher clamping force is induced in the verticaldirection and the frictional force increases proportionally.

FIG. 8 shows the appearance of the bottom surface of the wedge of thepresent invention.

As illustrated in FIG. 8, the bottom surface of the wedge (30) can bemechanically processed with various techniques in order to increase thecoefficient of friction. Though serrations of projection type (306) andfurrow type (308) are shown in the figure, different kinds of shapes canbe used.

FIG. 9 illustrates the shapes of the wedge in the present invention.

As described in FIG. 9, the wedge (30) can be formed in various shapes.Though triangle (31), pentagon (32), trapezoid (35), double pentagon(36), and the like are shown in the figure, different shapes can beused.

The wedge of No. 38 can be used in the case when the coupling device isdesigned to transfer external force applied monotonically. The wedge ofNo. 39 has a slope in the axial direction of the wedge in order to helpinstallation.

Wedges of a pentagon shape are used to illustrate the present invention.However, the scope of the present invention is not limited to thisshape.

Although it is desirable to conform the slope of the connecting slot tothat of the wedge (30), different shape can be used depending onconditions.

FIG. 10 shows the installation of the separate-type coupling caseaccording to the present invention. The upper one is an illustration ofthe dismantled state and the lower one is an illustration of theassembled state. The coupling case (20) is made in two pieces, which arejoined using bolts (14). This separate-type coupling case (20) can beused when one-body type is inconvenient to use.

FIG. 11 illustrates another separate-type coupling case different fromthat of FIG. 10. The two pieces of the coupling case (20) are joined bysliding the male piece into the female piece using connecting fragment(310). The male piece and the female piece can be tapered to helpinstallation.

FIG. 12 illustrates the coupling case of the present invention, whichcan resist external forces acting in two directions perpendicular toeach other.

As described in FIG. 12, this coupling case (20) has connecting slots inwhich wedges are placed in two directions perpendicular to each other toprevent the members from slipping out of the coupling case in eitherdirection. Each wedge resists external force applied in the directionperpendicular to the direction of the wedge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents the method 1 of the prior art;

FIG. 2 represents the problems of the method 1 of the prior art;

FIG. 3 represents the method 2 of the prior art;

FIGS. 4A and 4B represent the method 3 of the prior art;

FIGS. 5A and 5B illustrate the principle of operation according to thepresent invention;

FIGS. 6A and 6B show the coupling device of the present invention forconnecting members subjected to axial compression and/or tension force;

FIGS. 7A and 7B show the coupling device of the present invention forconnecting members subjected to shear force;

FIG. 8 illustrates the bottom surface of the wedge according to thepresent invention;

FIG. 9 illustrates various shapes of the wedge according to presentinvention;

FIGS. 10A and 10B show the separate-type coupling case of the presentinvention using bolts;

FIGS. 11A and 11B show the separate-type coupling case of the presentinvention using male and female pieces;

FIG. 12 shows the coupling case of the present invention for connectingmembers subjected to both axial and shear forces;

FIG. 13 represents the connection between two H-shaped members accordingto the present invention described in Preferred Embodiment 1;

FIG. 14 represents the connection between two H-shaped members that meetat right angle according to the present invention described in PreferredEmbodiment 2;

FIG. 15 represents the connection between two H-shaped members that meetat right angle according to the present invention described in PreferredEmbodiment 3;

FIG. 16 represents the connection between two H-shaped members that meetat right angle according to the present invention described in PreferredEmbodiment 4; and,

FIG. 17 represents the connection between two H-shaped members ofdifferent sizes according to the present invention described inPreferred Embodiment 5.

EXPLANATION OF SYMBOLS IN THE FIGURES

10: member

20: coupling case

30: wedge

306: projection

308: serration

40: elastic clipping plate

BEST MODE FOR CARRYING OUT THE INVENTION

Practical and presently preferred embodiments of the present inventionare illustrative as shown below.

However, it will be appreciated that those skilled in the art, onconsideration of this disclosure, may make modifications andimprovements within the scope of the present invention.

<Preferred Embodiment 1>

FIG. 13 illustrates Preferred Embodiment 1 of the present invention. Inthis figure, coupling device of the present invention are used toconnect two H-shaped members (10). The two coupling cases (20) toconnect the top flange are the type of coupling device exhibited in FIG.6, and the web is connected using the coupling device shown in FIG. 7,and the bottom flange is connected using the separate-type couplingdevice exhibited in FIG. 10. FIG. 13 shows that different types ofcoupling devices can be used for one joint depending on conditions,though it is not usual in construction field.

Other types of coupling cases (20) illustrated in FIG. 11 or FIG. 12 canbe applied in FIG. 13.

<Preferred Embodiment 2>

FIG. 14 illustrates Preferred Embodiment 2 of the present invention. Thecoupling device of the present invention connects two H-shaped members(10) that meet at right angle.

In this figure, the coupling case (20) has three connecting slots. Twoconnecting slots are used for one member (vertical member in the figure)to resist two external forces acting in two directions. One connectingslot is used for the other member (horizontal member in the figure) toresist external force in one direction.

<Preferred Embodiment 3>

FIG. 15 illustrates Preferred Embodiment 3 of the present invention.Compared with Preferred Embodiment 2, one member (horizontal member inthe figure) is rotated by 90° about its axis. Preferred Embodiment 3employs the coupling case (20) exhibited in FIG. 12 to resist externalforces in two directions.

<Preferred Embodiment 4>

FIG. 16 illustrates Preferred Embodiment 4 of the present invention. Inthis preferred embodiment, coupling case (20) of the present inventionhas a connecting slot on one side only. The other flat side is connectedto a member using bolts.

<Preferred Embodiment 5>

FIG. 17 illustrates Preferred Embodiment 5 of the present invention. Thecoupling device (20) of the present invention connects one member toanother of larger size which is welded to a column member using themethod of Preferred Embodiment 1.

As shown in the figure, the width and the thickness of two members aredifferent. Two members of different sizes can be connected by adjustingthe length and/or the height of the connecting slots. The couplingdevice of the present invention can be used to improve the seismicperformance of structural frame during severe earthquake by moving theplastic hinge away from the beam-to-column welds.

INDUSTRIAL APPLICABILITY

The coupling device of the present invention can solve the problems ofbolt connections such as a notch and stress concentration around theholes. Besides, the coupling device of the present invention can reducethe construction time and the labor costs greatly compared withfriction-type bolt connection.

Those skilled in the art will appreciate that the conceptions andspecific embodiments disclosed in the foregoing description may bereadily utilized as a basis for modification or design of otherembodiments to carry out the same purposes of the present invention.Those skilled in the art will also appreciate that such equivalentembodiments do not depart from the scope of the invention as set forthin the appended claims.

1. A coupling device for connecting members, comprising: a coupling casethat has at least one connecting slot which respectively receives one ofthe members; and wedges that are inserted into the spaces between saidcoupling case and each of said received members perpendicularly to thedirection of external pressure given to each of said members, whereineach of said wedges have one side and another side out of at least acouple of sloped sides contacting said coupling case in oppositedirections and have a higher coefficient of friction on a bottom sidesurface that touches one of said members than on the sloped sidesurfaces that touch said coupling case, wherein the bottom surface ofeach said wedge has projections or serrations parallel or almostparallel to the axis of said wedge to increase the friction coefficient.2. A coupling device for connecting members, comprising: a coupling casethat has at least one connecting slot which respectively receives one ofthe members; and wedges that are inserted into the spaces between saidcoupling case and each of said received members perpendicularly to thedirection of external pressure given to each of said members, whereineach of said wedges have one side and another side out of at least acouple of sloped sides contacting said coupling case in oppositedirections and have a higher coefficient of friction on a bottom sidesurface that touches one of said members than on the sloped sidesurfaces that touch said coupling case, wherein said wedges conform tothe space between said coupling case and said members and the crosssectional shape of each said wedge is selected among triangle,trapezoid, or pentagon, and wherein the bottom surface of each saidwedge has projections or serrations parallel or almost parallel to theaxis of said wedge to increase the friction coefficient.
 3. A couplingdevice for connecting members, comprising: a coupling case that has atleast one connecting slot which respectively receives one of themembers; and wedges that are inserted into the spaces between saidcoupling case and each of said received members perpendicularly to thedirection of external pressure given to each of said members, whereineach of said wedges have one side and another side out of at least acouple of sloped sides contacting said coupling case in oppositedirections and have a higher coefficient of friction on a bottom sidesurface that touches one of said members than on the sloped sidesurfaces that touch said coupling case, wherein said wedges conform tothe space between said coupling case and said members and the crosssectional shape of each said wedge is selected among triangle,trapezoid, or pentagon, wherein the wedge angle (θ) between the slopedside and the bottom side of each said wedge is ranged from 1° to$\left( {{atan}\frac{\mu^{\prime} - \mu}{1 + {\mu \cdot \mu^{\prime}}}} \right),$wherein μ is a friction coefficient between said wedge and said couplingcase; and μ′ is a friction coefficient between said wedge and saidmember, and wherein the bottom surface of each said wedge hasprojections or serrations parallel or almost parallel to the axis ofsaid wedge to increase the friction coefficient.
 4. A coupling devicefor connecting members, comprising: a coupling case that has at leastone connecting slot which respectively receives one of the members; andwedges that are inserted into the spaces between said coupling case andeach of said received members perpendicularly to the direction ofexternal pressure given to each of said members, wherein each of saidwedges have one side and another side out of at least a couple of slopedsides contacting said coupling case in opposite directions and have ahigher coefficient of friction on a bottom side surface that touches oneof said members than on the sloped side surfaces that touch saidcoupling case, wherein said wedges conform to the space between saidcoupling case and said members and the cross sectional shape of eachsaid wedge is selected among triangle, trapezoid, or pentagon, whereinthe wedge angle (θ) between the sloped side and the bottom side of eachsaid wedge is ranged from 1° to$\left( {{atan}\frac{\mu^{\prime} - \mu}{1 + {\mu \cdot \mu^{\prime}}}} \right),$wherein μ is a friction coefficient between said wedge and said couplingcase; and μ′ is a friction coefficient between said wedge and saidmember, wherein each said wedge also has slope in its axial direction tohelp installation, and wherein the bottom surface of each said wedge hasprojections or serrations parallel or almost parallel to the axis ofsaid wedge to increase the friction coefficient.